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Linux/fs/utimes.c

  1 #include <linux/compiler.h>
  2 #include <linux/file.h>
  3 #include <linux/fs.h>
  4 #include <linux/linkage.h>
  5 #include <linux/mount.h>
  6 #include <linux/namei.h>
  7 #include <linux/sched.h>
  8 #include <linux/stat.h>
  9 #include <linux/utime.h>
 10 #include <linux/syscalls.h>
 11 #include <linux/uaccess.h>
 12 #include <asm/unistd.h>
 13 
 14 #ifdef __ARCH_WANT_SYS_UTIME
 15 
 16 /*
 17  * sys_utime() can be implemented in user-level using sys_utimes().
 18  * Is this for backwards compatibility?  If so, why not move it
 19  * into the appropriate arch directory (for those architectures that
 20  * need it).
 21  */
 22 
 23 /* If times==NULL, set access and modification to current time,
 24  * must be owner or have write permission.
 25  * Else, update from *times, must be owner or super user.
 26  */
 27 SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
 28 {
 29         struct timespec tv[2];
 30 
 31         if (times) {
 32                 if (get_user(tv[0].tv_sec, &times->actime) ||
 33                     get_user(tv[1].tv_sec, &times->modtime))
 34                         return -EFAULT;
 35                 tv[0].tv_nsec = 0;
 36                 tv[1].tv_nsec = 0;
 37         }
 38         return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
 39 }
 40 
 41 #endif
 42 
 43 static bool nsec_valid(long nsec)
 44 {
 45         if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
 46                 return true;
 47 
 48         return nsec >= 0 && nsec <= 999999999;
 49 }
 50 
 51 static int utimes_common(const struct path *path, struct timespec *times)
 52 {
 53         int error;
 54         struct iattr newattrs;
 55         struct inode *inode = path->dentry->d_inode;
 56         struct inode *delegated_inode = NULL;
 57 
 58         error = mnt_want_write(path->mnt);
 59         if (error)
 60                 goto out;
 61 
 62         if (times && times[0].tv_nsec == UTIME_NOW &&
 63                      times[1].tv_nsec == UTIME_NOW)
 64                 times = NULL;
 65 
 66         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 67         if (times) {
 68                 if (times[0].tv_nsec == UTIME_OMIT)
 69                         newattrs.ia_valid &= ~ATTR_ATIME;
 70                 else if (times[0].tv_nsec != UTIME_NOW) {
 71                         newattrs.ia_atime.tv_sec = times[0].tv_sec;
 72                         newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
 73                         newattrs.ia_valid |= ATTR_ATIME_SET;
 74                 }
 75 
 76                 if (times[1].tv_nsec == UTIME_OMIT)
 77                         newattrs.ia_valid &= ~ATTR_MTIME;
 78                 else if (times[1].tv_nsec != UTIME_NOW) {
 79                         newattrs.ia_mtime.tv_sec = times[1].tv_sec;
 80                         newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
 81                         newattrs.ia_valid |= ATTR_MTIME_SET;
 82                 }
 83                 /*
 84                  * Tell setattr_prepare(), that this is an explicit time
 85                  * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
 86                  * were used.
 87                  */
 88                 newattrs.ia_valid |= ATTR_TIMES_SET;
 89         } else {
 90                 newattrs.ia_valid |= ATTR_TOUCH;
 91         }
 92 retry_deleg:
 93         inode_lock(inode);
 94         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 95         inode_unlock(inode);
 96         if (delegated_inode) {
 97                 error = break_deleg_wait(&delegated_inode);
 98                 if (!error)
 99                         goto retry_deleg;
100         }
101 
102         mnt_drop_write(path->mnt);
103 out:
104         return error;
105 }
106 
107 /*
108  * do_utimes - change times on filename or file descriptor
109  * @dfd: open file descriptor, -1 or AT_FDCWD
110  * @filename: path name or NULL
111  * @times: new times or NULL
112  * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
113  *
114  * If filename is NULL and dfd refers to an open file, then operate on
115  * the file.  Otherwise look up filename, possibly using dfd as a
116  * starting point.
117  *
118  * If times==NULL, set access and modification to current time,
119  * must be owner or have write permission.
120  * Else, update from *times, must be owner or super user.
121  */
122 long do_utimes(int dfd, const char __user *filename, struct timespec *times,
123                int flags)
124 {
125         int error = -EINVAL;
126 
127         if (times && (!nsec_valid(times[0].tv_nsec) ||
128                       !nsec_valid(times[1].tv_nsec))) {
129                 goto out;
130         }
131 
132         if (flags & ~AT_SYMLINK_NOFOLLOW)
133                 goto out;
134 
135         if (filename == NULL && dfd != AT_FDCWD) {
136                 struct fd f;
137 
138                 if (flags & AT_SYMLINK_NOFOLLOW)
139                         goto out;
140 
141                 f = fdget(dfd);
142                 error = -EBADF;
143                 if (!f.file)
144                         goto out;
145 
146                 error = utimes_common(&f.file->f_path, times);
147                 fdput(f);
148         } else {
149                 struct path path;
150                 int lookup_flags = 0;
151 
152                 if (!(flags & AT_SYMLINK_NOFOLLOW))
153                         lookup_flags |= LOOKUP_FOLLOW;
154 retry:
155                 error = user_path_at(dfd, filename, lookup_flags, &path);
156                 if (error)
157                         goto out;
158 
159                 error = utimes_common(&path, times);
160                 path_put(&path);
161                 if (retry_estale(error, lookup_flags)) {
162                         lookup_flags |= LOOKUP_REVAL;
163                         goto retry;
164                 }
165         }
166 
167 out:
168         return error;
169 }
170 
171 SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
172                 struct timespec __user *, utimes, int, flags)
173 {
174         struct timespec tstimes[2];
175 
176         if (utimes) {
177                 if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
178                         return -EFAULT;
179 
180                 /* Nothing to do, we must not even check the path.  */
181                 if (tstimes[0].tv_nsec == UTIME_OMIT &&
182                     tstimes[1].tv_nsec == UTIME_OMIT)
183                         return 0;
184         }
185 
186         return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
187 }
188 
189 SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
190                 struct timeval __user *, utimes)
191 {
192         struct timeval times[2];
193         struct timespec tstimes[2];
194 
195         if (utimes) {
196                 if (copy_from_user(&times, utimes, sizeof(times)))
197                         return -EFAULT;
198 
199                 /* This test is needed to catch all invalid values.  If we
200                    would test only in do_utimes we would miss those invalid
201                    values truncated by the multiplication with 1000.  Note
202                    that we also catch UTIME_{NOW,OMIT} here which are only
203                    valid for utimensat.  */
204                 if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
205                     times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
206                         return -EINVAL;
207 
208                 tstimes[0].tv_sec = times[0].tv_sec;
209                 tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
210                 tstimes[1].tv_sec = times[1].tv_sec;
211                 tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
212         }
213 
214         return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
215 }
216 
217 SYSCALL_DEFINE2(utimes, char __user *, filename,
218                 struct timeval __user *, utimes)
219 {
220         return sys_futimesat(AT_FDCWD, filename, utimes);
221 }
222 

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